Idea from snappycreeper: https://github.com/snappycreeper/OldDiscordFont
BetterDiscord (https://betterdiscord.app/)
Copy the Discord-s-new-font-sucks.css into the betterdiscord themes folder.
OpenAsar (https://openasar.dev/)
Go into the openasar settings, click theming and paste the code inside of Discord-s-new-font-sucks.css.
Sadly, there's no compatibility.
I don't know, maybe it can be adapted.
If you didn't know, discord changed its font from Whitney (Wonderful font) to GG Sans (a font created by discord that sucks). This custom css replaces the new font with the old one.
The old font, Whitney, was not owned by discord and must be paid to be used. So discord, after years of using Whitney, decided to create its own font, GG Sans, which sucks in many ways.
A similar plugin already exists, created by snappycreeper. This plugin does the same thing only I encountered problems, this one should be bug free.